A former partner of Kenneth Griffin, the founder of Citadel Investment Group, has dropped a lawsuit accusing him of fraud, breach of a partnership agreement and misappropriation of trade secrets.

Rush Simonson, a former business partner of Griffin, filed a suit in June claiming the hedge fund mogul stole trading software and strategies the two developed for two hedge funds they managed in the 1980s. The proprietary software and strategies have been used to drive Citadel’s success, Simonson alleged in the suit.

Last week, Simonson withdrew his complaint and a Florida district court judge dismissed the lawsuit. In a letter to Griffin, Simonson apologized to his former business partner.

“I have appreciated your efforts to be forthright and cordial in resolving this matter and I apologize for any harm the filing of this suit has caused you,” Simonson said in his letter.

Both Griffin and Simonson said in separate statements that Simonson was not compensated for dropping his lawsuit. In his statement, Griffin said the withdrawal of the complaint and dismissal of the case are a testament to the power of the truth.

“I honored my contractual and fiduciary duties to Mr. Simonson, our partnerships, and to all of the limited partners. The dissolution and termination of the two partnerships and of the business relationship between Mr. Simonson and me, which was completed shortly after I graduated from college, was legal and orderly. The allegations made by Mr. Simonson in the litigation were false,” Griffin said in a statement.

Simonson said he was a friend and mentor to Griffin in the 1980s. The two men formed a partnership and launched two convertible arbitrage hedge funds while Griffin was still a student at Harvard University. Simonson said he quit his brokerage job to solicit investors, run the operations, formulate the investment policy and review early trades while Griffin traded. Griffin allegedly needed Simonson’s business sense and contacts to attract investors in the funds, the suit claims.

Griffin and Simonson launched their first fund in 1987 and launched a second in 1988. The second fund used software developed by Simonson to “quickly identify and exploit arbitrage opportunities.”

Griffin later moved to Chicago and formed his own firm. He also convinced Simonson to dissolve their hedge funds. The lawsuit claimed Griffin used the software and trading programs he developed with Simonson during their partnership to build Citadel. Because of his allegedly fraudulent actions concerning their partnership and his continued use of their proprietary trading programs and software, Simonson claimed he was entitled to a share of the profits generated by the $13bn (€9.9bn) hedge fund firm.